1. Field of the Invention
This invention is directed to vibratory separators; shale shakers; screens and screen assemblies for them; and methods of their use.
2. Description of Related Art
Vibrating screens have been employed for many years to separate particles in a wide array of industrial applications. One common application of vibrating screens is in drilling operations to separate particles suspended in drilling fluids. The screens are mounted generally horizontally on a vibrating mechanism or shaker that imparts a desired motion to the screen. Material from which particles are to be separated is poured onto a back end of the vibrating screen, usually from a pan mounted above the screen. The material generally flows toward the front end of the screen. Large particles are unable to move through the screen remaining on top of the screen and moving toward the front of the screen where they are collected. The smaller particles and fluid flows through the screen and collects in a tank, receptacle or pan beneath the screen.
Typically a vibrating screen is resiliently suspended or mounted upon a support and is caused to vibrate by a vibrating mechanism, e.g. an unbalanced weight on a rotating shaft connected to a basket or frame. The screen is vibrated by vibratory equipment to create a flow of trapped solids on top surfaces of the screen for removal and disposal of solids. The fineness or coarseness of the mesh of a screen may vary depending upon mud flow rate and the size of the solids to be removed.
The need for solids control in drilling mud used in hydrocarbon well drilling is well known in the prior art. Drilling mud, typically a mixture of clay and water and various additives, is pumped down through a hollow drill string (pipe, drill collar, bit, etc.) into a well being drilled and exits through holes in a drillbit. The mud picks up cuttings (rock) and other solids from the well and carries them upwardly away from the bit and out of the well in a space between the well walls and the drill string. At the top of the well, the solids-laden mud is discharged over a shale shaker, a device which typically has a screen or a series of screens arranged in tiered or flat disposition with respect to each other. The prior art discloses a wide variety of vibrating screens, devices which use them, shale shakers, and screens for shale shakers. The screens catch and remove solids from the mud as the mud passes through them. If drilled solids and/or debris are not removed from the mud used during the drilling operation, recirculation of the drilled solids can create weight, viscosity, and gel problems in the mud, as well as increasing wear on mud pumps and other mechanical equipment used for drilling.
In many cases it is difficult if impossible to mount or hang a screen S in a vibratory separator or shale shaker so that the lateral plane of its surface is perfectly horizontal. Either the center of the screen bulges upward laterally from the longitudinal edges of the screen as shown in FIG. 1 (an xe2x80x9cover slungxe2x80x9d screen as described in U.S. Pat. No. 4,820,407, incorporated fully herein), in which case the screen is said to be xe2x80x9ccrownedxe2x80x9d or xe2x80x9cover slungxe2x80x9d, or the center bulges downward in which case the screen is said to be xe2x80x9cunder slungxe2x80x9d. A screen that is xe2x80x9ccrownedxe2x80x9d or xe2x80x9cover slungxe2x80x9d (FIG. 1), causes solids to tend to congregate at the screen""s longitudinal edges; if a screen is xe2x80x9cunder slungxe2x80x9d, solids tend to congregate at its center.
FIG. 2 shows a typical prior art vibratory separator system A with a screen B (with screen or screening cloth or mesh as desired) according to the present invention mounted on vibratable screen mounting apparatus or xe2x80x9cbasketxe2x80x9d C. The screen B may be any screen disclosed herein or have any combination of any feature or features of any screen or screen part disclosed herein; and any such screen may be used with any appropriate shaker or screening apparatus. The basket C is mounted on springs I (only two shown; two as shown are on the opposite side) which are supported from a frame D. The basket C is vibrated by a motor E and interconnected vibrating apparatus F which is mounted on the basket C for vibrating the basket and the screens. Elevator apparatus G provides for raising and lowering of the basket end. The screen B is any prior art screen, screens, and/or screen assembly.
FIG. 3 shows a prior art screen mounting basket J with a screen K mounted therein with a typical prior art xe2x80x9ccrownxe2x80x9d disposition with a middle crown portion L. Typical mounting rails or channels M are used with typical mounting devices N to releasably secure the screen K in the basket J.
There has long been a need recognized by the present inventor for a vibratory separator screen which overcomes the problems of prior art crowned screens.
The present invention discloses, in at least certain embodiments, screens and screen assemblies for vibratory separators (including, but not limited to screens for shale shakers for treating drilling fluid or xe2x80x9cmudxe2x80x9d) and vibratory separators with such screens and screen assemblies. In certain aspects screen assemblies according to the present invention have one or more screening members (screen, mesh, perforated plate, etc.) with a top surface that is higher in the middle than at one or both ends, i.e., when viewed from the side one or both ends of the screen assembly are at a level below the screen assembly""s middle. In certain aspects the surface tapers from the middle down to the end(s). The xe2x80x9cendsxe2x80x9d of the screen assembly are a first end onto which material to be treated (e.g., but not limited to, drilling fluid from which mud is to be filtered) is introduced to the screen assembly and a second end from which separated material (e.g., but not limited to, solids like drilled cuttings and/or debris) exits from the vibratory separator.
In certain particular embodiments an exit end of such a screen assembly is positioned over a lower screen assembly and separated solids (which may still have some liquid therein) fall down onto the lower screen. The lower screen may be any known two-or three-dimensional screen and it may be, in particular aspects formed with a higher middle and one or both lower ends according to the present invention.
Any screen or screen assembly known in the prior art may be formed according to the present invention with a relatively higher middle and with one or both ends lower than the middle (in side view).
In certain embodiments the present invention discloses a vibratory separator with a screen or screens according to the present invention as described herein.
In other aspects a screen is mounted in a basket or screen cradle of a vibratory separator so that part of the screen is higher than one or both ends. In one aspect such a screen has sufficient flexibility to be bent into a desired configuration; in other aspects the screen is made in the desired configured or multiple sub-screens and/or screen parts are positioned in the desired shape. Screens mounting or holding devices or apparatuses are used to hold the screen or screens in the desired shape (viewed from the side).
To the extent more screening area is available with a screen assembly according to the present invention, screening efficiency and capacity are increased.
In certain aspects, the present invention discloses a vibratory separator for separating components of material introduced to the vibratory separator (which in one aspect is a shale shaker for separating drilling fluid from a mixture of drilling fluid, drilled cuttings, debris, etc.), the vibratory separator having a basket for holding screening apparatus; vibrating apparatus for vibrating the screening apparatus; screening apparatus mounted in the basket, the screening apparatus having at least a first portion and a second portion, the first portion lower in the basket than the second portion, and receptacle apparatus below the screening apparatus for receiving material components flowing through the screening apparatus.
With a vibratory separator according to the present invention a pond or pool can be formed at, e.g., the first screen end at which material is introduced to the vibratory separator. In certain aspects this pool has a relatively increased pressure head that drives liquid through screen adjacent the pool. The size of the pool can be adjusted by adjusting the height of the screen end. Apparatus may be provided to adjust screen end height in a basket to adjust pool depth and size.
What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain preferred embodiments of the invention, other objects and purposes will be readily apparent to one of skill in this art who has the benefit of this invention""s teachings and disclosures. It is, therefore, an object of at least certain preferred embodiments of the present invention to provide:
New, useful, unique, efficient, nonobvious devices and methods for vibratory separators and shale shakers;
Such separators and shakers with a screen or screens mounted therein with at least one end part lower than other parts of the screen when viewed from the side;
Such separators and shakers with such a screen above an end of which forms a pool of material to be treated by the separator or shaker; and
New, useful, unique, efficient and nonobvious screens and screen assemblies for such separators and shakers;
Such screens and screen assemblies with a xe2x80x9ccrownxe2x80x9d in the middle when viewed from a side; and
New, useful, unique, efficient and nonobvious methods for using such separators, shakers, and screens.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention.
The present invention recognizes and addresses the previously-mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one skilled in this art who has the benefits of this invention""s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent""s object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.